Their fossilized shells formed these limestone rocks, which, like Gubbio's mountains, were once at the bottom of the ocean. Now exposed, they represent over a million years of a geological time period known as the Cretaceous.
Walter Alvarez found that forming a distinct boundary between the limestone of the two periods was a thin layer of red clay. Immediately below this clay boundary, the Cretaceous limestone was heavily populated with a wide mix of the fossils of tiny marine creatures called foraminifera, or “foram” for short.
On the Atlantic Coast, outside the town of Zumaia, Dutch geologist Jan Smit was studying the forams from a different ancient sea. Their fossilized shells formed these limestone rocks, which, like Gubbio's mountains, were once at the bottom of the ocean.
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Answer:
A) Sample B has more calcium carbonate molecules
Explanation:
M = Molar mass of calcium carbonate = 100.0869 g/mol
= Avogadro's number = 
For the 4.12 g sample
Moles of a substance is given by

Number of molecules is given by

For the 19.37 g sample

Number of molecules is given by


So, sample B has more calcium carbonate molecules.
The ratio of the elements of carbon, oxygen, calcium atoms, ions, has to be same in both the samples otherwise the samples cannot be considered as calcium carbonate. Same is applicable for impurities. If there are impurites then the sample cannot be considered as calcium carbonate.
Answer: yes
Explanation: Radioactive (or nuclear) waste is a byproduct from nuclear reactors, fuel processing plants, hospitals and research facilities. Radioactive waste is also generated while decommissioning and dismantling nuclear reactors and other nuclear facilities. There are two broad classifications: high-level or low-level waste.
To find how many moles of the gas you can use ideal gas formula. Remember to change the temperature unit to Kelvin. Since the pressure using kpa, the constant used would be 8.314 kpa*L / mol*K
PV=nRT
n= PV/RT
n= 17,250 kpa * 20 / 8.314 * (24+273.15)K
n=139.64moles